As embattled former Port Authority Chairman David Samson sues to head off an Ethics Commission probe, the Christie administration finds itself in the awkward position of defending the ethics agency against a man who was a key ally of the governor.

Samson, a former New Jersey attorney general who chaired Gov.-elect Christie's transition team in 2009 and was later appointed chairman of the Port Authority of New York and New Jersey, asked a federal judge to declare that the Ethics Commission lacks jurisdiction to investigate or act against him in his capacity as a member of the bistate agency's board.

The lawsuit, filed Monday in U.S. District Court in Trenton, comes as the U.S. Attorney's Office continues to investigate the George Washington Bridge lane closure scandal, which heaped scrutiny on the governor's office and the Port Authority, while also spawning inquiries into Samson's business dealings.

The ethics investigation was prompted by a complaint filed in March by the New Jersey Working Families Alliance, which alleges that Samson violated state conflicts-of-interest law by using his position at the Port Authority to help his law firm's clients.

On Wednesday, the group's director, Analilia Mejia, said there "must be appropriate safeguards put in place to ensure that the attorney general is not politically influenced by Gov. Christie in how he responds" to the lawsuit.

She added that Samson's lawsuit "conveniently omits key provisions of the Port Authority Code of Ethics and New Jersey state law that place his actions clearly within the reach of New Jersey's ethics law."

The alliance, a coalition of unions and environmental groups, says it is a grassroots political nonprofit that seeks to advance progressive policies.

Christie nominated Samson to head the Port Authority in 2011. When Samson resigned in March in the aftermath of the lane-closure controversy, Christie told reporters, "I have every faith and trust and confidence in David's integrity, as do people on both sides of the aisle in this state over the course of the past 40 years."

In defending the Ethics Commission against Samson, the administration is now in "a bit of a tough spot" from "a public perception point of view," given Christie's close ties to the former port chief, said Carl Golden, a former press secretary to Govs. Thomas H. Kean and Christie Whitman, and now a senior contributing analyst at the William J. Hughes Center for Public Policy at Richard Stockton College.

However, the attorney general likely won't argue the merits of the investigation, since the lawsuit is simply a matter of jurisdiction, Golden said.

"It's a small world inside the Trenton beltway, so I don't think it's that big a deal," said Ben Dworkin, director of the Rebovich Institute for New Jersey Politics at Rider University.

The suit, filed by Samson and his firm, says the Ethics Commission served a subpoena on the firm, Wolff & Samson, in October "for documents in connection with" the investigation.

The seven-member Ethics Commission, which includes three gubernatorial appointees, administers and enforces state conflict-of-interest law. Mark Holmes, the board's deputy director, referred comment to the Attorney General's Office, which confirmed it would represent the commission but declined further comment.

Samson, who was attorney general under Democratic Gov. Jim McGreevey, alleges the Port Authority's own code of ethics governs conflicts of the bistate agency's commissioners, "not the laws of either the state of New Jersey or New York."

Only bistate legislation passed by both states and signed by both governors can override the Port Authority's internal rules, the suit says. It points to legislation that passed both legislatures this year "to address these very issues."

The legislation sits before Christie and New York Gov. Andrew Cuomo. Among other provisions, it would prohibit commissioners from voting on proposals that may raise a conflict of interest.